PHYLOGENY OF THE GRASSLAND LEAFHOPPER GENUS FLEXAMIA (HOMOPTERA, CICADELLIDAE) BASED ON MITOCHONDRIAL-DNA SEQUENCES

Leafhoppers (Cicadellidae) are a highly diverse group of sap-sucking i nsects, many species of which specialize on grasses. Past attempts to examine the roles of host transfer or host plant coevolution in the di versification of leafhopper species using cladistic methods have been hindered by a paucity of discrete, phylogenetically informative morpho logical characters. To demonstrate the utility of DNA sequence data fo r species-level phylogenetic studies of Cicadellidae, we estimated phy logenetic relationships among species in the North American grassland leafhopper genus Flexamia DeLong using partial nucleotide sequences of mitochondrial 16S rDNA and NADH dehydrogenase 1, totaling 1496 base p airs and 810 potentially informative characters. Analyses of the parti tioned and combined sequence data using maximum parsimony, neighbor-jo ining, and maximum likelihood criteria yielded similar estimates of re lationships in which most nodes were well-supported by bootstrap and d ecay indices. These estimates largely agreed with a previously publish ed, intuitive, morphology-based phylogeny for the genus. A parsimony r econstruction of host associations based on these results suggests tha t the origins of various flexamia clades coincided with host transfers among grass subfamilies or genera, Nevertheless, associations with ce rtain subfamilies, genera, or species of grasses appear to have been l argely conserved in the evolutionary diversification of flexamia. (C) 1997 Academic Press.